Oral Presentation
Properties of low-mass Hα emitters at z ∼ 2.3 from broad-band selection in the ZFOURGE Survey
Presenter: Nuo Chen (The University of Tokyo)
We investigate the properties of ∼1300 Hα emitters (HAEs) at z ∼ 2.3, selected from the flux excess in the ZFOURGE Ks broad-band data to the best-fit stellar continuum. A large population of low-mass Hα emitters is identified from their elevated SFR(Hα) above the star formation main sequence (SFMS) in low-mass regime. The 401 low-mass HAEs in our work may be an analog population of the galaxies that reionized the universe at the epoch of reionization. The hydrogen ionizing photon production efficiencies, ξion, of the low-mass HAEs have a median value
of log(ξion/erg−1Hz) = 25.24 (25.35), assuming the Calzetti (SMC) curve for the stellar continuum dust correction, higher than that of the main sequence galaxies by ∼0.2 dex at similar redshift. This indicates that the low-mass HAEs are more efficient in producing ionizing photons. We then discuss the dependence between ξion and UV spectral slope (βUV), UV magnitude (MUV), the equivalent widths of Hα and [Oiii] emission lines. Galaxies with the bluest UV slope, faintest UV luminosity and highest equivalent width would have elevated ξion by a factor of ∼2 than the median ξion of our sample. We further compare the low-mass HAEs with other possible LyC-leaking candidates (LAEs) on their ionization states, IGM environment and put forward an "Iceberg" model to relate these populations. With the large release of JWST data, our method and these new findings would provide new implication to the low-mass galaxies at higher redshift and even the epoch of reionization.
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